1. Field of the Invention
This invention relates generally to the control of flow and pressure relief functions in a pump and more particularly relates to a pump having an integral flow control arrangement incorporated therein.
2. Description of the Prior Art
The prior art is replete with pumps having integral flow control valves. However, most of these require the valve structure to by-pass the full pump output to inlet. Sometimes such a flow control valve is located exteriorly of the pump in a conduit leading to the point of utilization. In other forms of pump construction, the flow control valve is made a part of the pump package by being incorporated directly in passages of a pump housing, or in still other instances as an integral part of various components combined in a pumping cartridge. In either case, internal valve by-pass at top speeds may result in 30 to 40 gpm flowing through the valve with resulting high Bernoulli reaction forces developing. These forces require high counter spring forces to close the ports without sticking or valve hysteresis. Added spring force results in significant increases in flow orifice pressure drop and its outward token, heat rise; the latter resulting in significant cost imposts for oil coolers to secure safe heat levels, that will prevent component wear and hose failures.
Many means for limiting the tendency toward end seizure have been used in the art. Fixed end clearances carefully monitored by quality control methods are difficult to control and represent the largest single end sealing means. Flexible end plates made of bronze or other premium materials have also been successfully applied at cost premium to various designs. Neither alternative is totally ideal.